If we know the volume equals 4 thirds π R cubed, we want to figure out what rate does the volume change with respect to the radius. So we're going to find DVDRDVDR is just really the 1st derivative SO4 Pi R-squared. We're going to stick R in at 5:00 to get 100 Pi. Now the second part actually says using the rate from part A by approximately how much does the volume increase when the radius changes from 5 to 5.4 inches? We're going to use part A, but we're actually going to go back to the original and think about how's the volume changing in terms of time. So if we thought about DV in terms of time, DVDT would equal the derivative for Pi R-squared as the radius changes in terms of time or DRDT. So when we look at this, we're really asking how's the volume changing in respect to some time where the time is what it took to go from 5 to 5.4 in the radius. So we'd have four Pi, the radius is still 5 ^2, but now our DRDT our our radius changing in terms of time was .4. So if we plug that in, we get 125.66 inches cubed.